A distribution list copies one message into many inboxes. A shared mailbox is one inbox that many people open. A Microsoft 365 group is a group mailbox with a workspace attached. All three give a team an address like support@ or sales@, and they behave differently the moment someone replies.
Use a distribution list to broadcast: announcements, notifications, anything nobody needs to answer. Use a shared mailbox when a team must read and reply from one address and see the same Inbox. Use a Microsoft 365 group when the same people also need files, a calendar and Teams, or when outside guests must be members. None of the three records who owns a reply or what was promised.
| Shared mailbox | Distribution list | Microsoft 365 group | |
|---|---|---|---|
| What it is | One mailbox that several licensed users open from their own accounts | An address that delivers each message to every member's own inbox | A group mailbox plus a SharePoint site, Planner, a calendar and optional Teams |
| Who sees replies | Everyone with Full Access, in the shared Inbox | Only the people on the reply; the list itself keeps nothing | Members, in the group's conversations; subscribers also get a copy |
| Sent Items | Sender's own Sent Items by default; an admin can copy them to the shared mailbox | Sender's own Sent Items; the list has no folders | The group mailbox keeps the conversation |
| Who can send from the address | Members with Send As or Send on Behalf | Delegates with Send As or Send on Behalf; otherwise replies come from the member | Members, if the admin enables send as or send on behalf |
| License | None up to 50 GB; Exchange Online Plan 2 for 100 GB, an archive or litigation hold | None; it is a directory object | None for the group; members need their own licenses |
| Limits | 50 GB unlicensed, 25 users, internal members only, no direct sign-in | Up to 100,000 members; counts as one recipient toward the 10,000 per day rate limit | Guests allowed; owners can delete group mail, members cannot |
| Best for | A team answering one address together | One-way announcements to a fixed audience | A project or department that needs mail plus files and meetings |
What is the difference between a shared mailbox and a distribution list?
The difference is where the message lives after delivery. A distribution list has no storage. Exchange expands the list, drops a copy of the message into each member's mailbox, and forgets it. If Priya replies, the reply comes from Priya's address, lands in Priya's Sent Items, and the other members never see it unless she copies the list.
A shared mailbox stores the message once. Every member with Full Access opens the same Inbox and sees the same read state. Anyone who also holds Send As or Send on Behalf can reply from the shared address.
Microsoft's summary: a shared mailbox is for multiple people who need access to the same mailbox, such as a company information or support address. Distribution groups are used for sending notifications to a group of people. Both definitions are on Compare types of groups in Microsoft 365, verified October 2026.
What a distribution list is
A distribution list, called a distribution group in the Exchange admin center, is a mail-enabled directory object with an address and a member list. Admins create it under Recipients > Groups > Distribution list, and it must have at least one owner. By default only senders inside the organization can mail it; the admin can open it to outside senders under Delivery management.
Members receive each message in their own Inbox and can file, flag or delete their copy without affecting anyone else. An admin can name delegates with Send As or Send on Behalf for the list, so a reply can appear to come from the list address. Nothing records which member answered.
The Exchange Online recipient rate limit counts a list in the address book as one recipient. That is why an announcement to a 400-person list does not consume 400 of the 10,000 recipients a mailbox can send to per day. Facts from Create and manage distribution groups and Exchange Online limits.
What a shared mailbox is
A shared mailbox is a real Exchange Online mailbox with a system-generated password nobody knows. Members never sign in to it. They open it from their own licensed account, in any Outlook client. The steps are in how to add a shared mailbox in Outlook.
It stores up to 50 GB without a license and supports a maximum of 25 users before Microsoft warns of connection failures and duplicated messages. Members must be inside your organization. It ships with a shared calendar. Replies sent as the mailbox land in the sender's own Sent Items unless an admin turns on the copy setting. How to send email from a shared mailbox covers that setting.
The full list of limits is on About shared mailboxes. Our limits, licensing and best practices guide works through what each one means for a team.
What a Microsoft 365 group is
A Microsoft 365 group is a membership object. It provisions a group mailbox, a SharePoint site, a Planner plan and a shared calendar at once, and can be connected to Microsoft Teams. Mail sent to the group address lands in the group mailbox, where members read it as conversations. Members who subscribe also get a copy in their own Inbox, and deleting that copy leaves the group's copy intact.
Groups can hold guests from outside the organization if an admin allows it, which a shared mailbox cannot. Group owners can delete any message in the group inbox; members can only delete conversations they started, and only in Outlook on the web.
Microsoft is explicit that a shared mailbox cannot be migrated to a Microsoft 365 group, so the choice is made at creation time. Steps for creating one are in how to create an email group in Outlook.
Shared mailbox vs user mailbox
A user mailbox is one licensed person's mailbox, 50 or 100 GB depending on the plan, with sign-in, encryption and an archive where the plan includes one. A shared mailbox is unlicensed, capped at 50 GB, and opened only through members' accounts.
Admins often convert a departing employee's user mailbox to a shared mailbox so the team keeps the history. The license can then be removed if the mailbox is under 50 GB. The steps and the catches are in how to create a shared mailbox in Microsoft 365.
When to use which
- Pick a distribution list when nobody needs to reply, or when replies are personal: all-staff announcements, a building notice list, a vendor notification address that feeds another system.
- Pick a shared mailbox when a small team must answer one address and see each other's replies. Think support@, billing@, a reception desk, or an account team's client address.
- Pick a Microsoft 365 group when the same people need the mail and the files and the meetings, when guests must be members, or when membership will pass 25 people.
- Pick a shared mailbox over a group when you want one shared Inbox with folders and categories. A group creates a SharePoint site and a Teams option alongside it, whether you want them or not.
A common mistake is a distribution list standing in for a team inbox. Five account managers on sales@ each get the client's message, each assumes someone else has it, and either two reply or none do. The list cannot tell you which happened because it kept nothing.
Switching to a shared mailbox fixes the record. Microsoft documents the conversion, though there is no automated path. The list's address has to be freed first, then the mailbox is created with the same address and members. See Convert a distribution list to a shared mailbox.
When neither is enough
A shared mailbox solves visibility. It does not solve ownership. There is still no field that says who is handling a thread, no internal note, and no view of what was promised to a client and when. Teams add categories named after people and a weekly reminder to check the Inbox, and that holds until volume grows.
At that point there are two kinds of tool. Help desks such as Help Scout are built for support queues and ticket volume. Mail is forwarded in and each message becomes a ticket, which suits a support address with mostly new names.
Front covers email, chat, SMS and social channels for omnichannel customer operations, with workspace setup to match. Missive blends email and team chat into one new app that the whole team moves into. Each adds assignment. None keeps a record of what a specific client was promised across months of threads. The comparison pages cover each in more detail.
We build Sektra, the shared inbox tool in that list for teams whose inbound is the same clients writing again. It is a separate workspace that syncs two-way with Outlook and Microsoft 365, shared mailboxes included. The mailbox stays where it is, and colleagues who never open Sektra still see the same state in Outlook.
Each thread gets an owner and notes. The memory layer is the record Sektra builds per contact of commitments made, questions left open and the people involved. It answers what we promised them without a search through three Sent folders. The Outlook integration page has the setup, and where an Outlook shared mailbox stops has the longer argument. Sektra for agencies describes the client-address-per-account setup where this matters first.
